-The objective of this study was to estimate genetic parameters for survival and weight of Nile tilapia (Oreochromis niloticus), farmed in cages and ponds in Brazil, and to predict genetic gain under different scenarios. Survival was recorded as a binary response (dead or alive), during harvest time in the 2008 grow-out period. Genetic parameters were estimated using a Bayesian mixed linear-threshold animal model via Gibbs sampling. The breeding population consisted of 2,912 individual fish, which were analyzed together with the pedigree of 5,394 fish. The heritabilities estimates, with 95% posterior credible intervals, for tagging weight, harvest weight and survival were 0.17 (0.09-0.27), 0.21 (0.12-0.32) and 0.32 (0.22-0.44), respectively. Credible intervals show a 95% probability that the true genetic correlations were in a favourable direction. The selection for weight has a positive impact on survival. Estimated genetic gain was high when selecting for harvest weight (5.07%), and indirect gain for tagging weight (2.17%) and survival (2.03%) were also considerable.Index terms: Oreochromis niloticus, correlation, fish genetic improvement, Gibbs sampling, GIFT strain, heritability. Parâmetros genéticos bayesianos para peso corporal e sobrevivência de tilápias-do-nilo cultivadas no BrasilResumo -O objetivo deste trabalho foi estimar parâmetros genéticos para a sobrevivência e peso de tilápias-do-nilo (Oreochromis niloticus), cultivadas em tanques-rede e viveiro de terra no Brasil, e predizer o ganho genético sob diferentes cenários. Mediu-se a sobrevivência como uma característica binária (peixe vivo ou morto), no período de crescimento de 2008 até a despesca. Os paramêtros genéticos foram estimados pelo modelo animal limiar-linear em análise bayesiana, pela amostragem de Gibbs. A população avaliada foi de 2.912 peixes individuais, que foram analisados juntamente com o pedigree de 5.394 peixes. As herdabilidades, com intervalos de credibilidade de 95%, obtidas para peso à identificação, peso à despesca e sobrevivência foram 0,17 (0,09-0,27), 0,21 (0,12-0,32) e 0,32 (0,22-0,44), respectivamente. Intervalos de credibilidade mostram 95% de probabilidade de que as verdadeiras correlações genéticas estejam em uma direção favorável. A seleção para peso tem impacto positivo na sobrevivência. O ganho genético estimado foi alto para a seleção quanto ao peso à despesca (5,07%), e o ganho indireto para o peso à identificação (2,17%) e à sobrevivência (2,03%) também foram consideráveis.Termos para indexação: Oreochromis niloticus, correlação, melhoramento genético de peixes, amostragem de Gibbs, linhagem GIFT, herdabilidade.

Weight gain and morphometric growth of the genetically improved tambaqui (Colossoma macropomum) are evaluated. Current assay was carried out on the Fish Farm Experimental Station of the Federal University of Mato Grosso, in the municipality of Santo Antonio de Leverger -MT Brazil. Seven fish families from the breeding program and a control group (not genetically improved) were evaluated. All animals were individually identified with a transmitter-responder label (transponder). Weight gain, overall and standard length, head size, height, width and body perimeter were measured. A completely randomized design was used and comparisons among families and the control group were carried out by Dunnett test at 5% significance level. The genetically improved fish families showed a 14.8% higher weight gain when compared to that of control group. Five out of seven families showed greater weight gain when compared to control group, with the best family exhibiting a 24.8% higher rate. Four families had higher growth in all evaluated morphometric characteristics when compared to control group. Only one family did not differ in any of the evaluated characteristics with regard to the control group. Key words: Genetic improvement of fish. Fish of the Amazon basin. Genetic selection. e um grupo controle (não melhorado geneticamente). Todos os animais foram individualizados com transponder. Foram mensurados o ganho de peso, comprimento total e padrão, tamanho de cabeça, altura, largura e perímetro do corpo. Utilizou-se delineamento inteiramente casualizado e as comparações entre as famílias e o grupo controle foram realizadas pelo teste de Dunnett com 5% de significância. As famílias melhoradas geneticamente apresentaram ganho de peso 14,8% superior ao grupo controle. Cinco das sete famílias avaliadas apresentaram maior ganho de peso em relação ao grupo controle, sendo que a melhor família foi superior em 24,8%. Quatro famílias apresentaram maior crescimento em todas as características morfométricas avaliadas em relação ao controle. Apenas uma família não diferiu em nenhuma das características avaliadas em relação ao grupo controle. Palavras-chave: Melhoramento genético de peixes. Peixe da bacia amazônica. Seleção genética. Resumo

Was evaluated the pattern of growth among females and males of tambaqui by Gompertz nonlinear regression model. Five traits of economic importance were measured on 145 animals during the three years, totaling 981 morphometric data analyzed. Different curves were adjusted between males and females for body weight, height and head length and only one curve was adjusted to the width and body length. The asymptotic weight (a) and relative growth rate to maturity (k) were different between sexes in animals with ± 5 kg; slaughter weight practiced by a specific niche market, very profitable. However, there was no difference between males and females up to ± 2 kg; slaughter weight established to supply the bigger consumer market. Females showed weight greater than males (± 280 g), which are more suitable for fish farming purposes defined for the niche market to larger animals. In general, males had lower maximum growth rate (8.66 g / day) than females (9.34 g / day), however, reached faster than females, 476 and 486 days growth rate, respectively. The height and length body are the traits that contributed most to the weight at 516 days (P <0.001).

This work evaluated the incorporation of dimethyl sulphoxide (DMSO) into the medium used for storing rainbow trout semen at 4°C for 13 days. The treatments used were: fresh semen as control (C); semen stored without dilution (T1); semen diluted in saline solution (0.2% KCl and 0.7% NaCl) (T2); T2 + DMSO 1% (T3); T2 + DMSO 2.5% (T4) and T2 + DMSO 5% (T5). Sperm motility (level and duration) and fertility were evaluated in all the treatments. The results show that at day 3, all the treatments maintained level 3 motility. After 5 days in storage, only T4 and T5 fell to level 2 motility. The maximum duration of flagellar activity was in T3 with 70.0 AE 2.14 s, and the minimum in T4 with 51.73 AE 0.29 s. At day 7, the fertility of T3 and T4 was maintained with no statistically significant differences from T2 (96.6 AE 2.5%), however, the fertility of T5 was 53.2 AE 11.8%. At day 13 the fertility of T3, the only treatment which remained fertile, was 68.8 AE 5.09%. The results show that the sperm fertility of semen stored with a low concentration of 1% DMSO is prolonged significantly.

In this work, the seminal parameters of P. mesopotamicus were evaluated fresh and after cryopreservation, focusing on the sperm variables that affect the rates of fertilization, hatching and post-hatching parameters such as larval survival and morphology. The semen and oocytes from the animals were collected after extrusion, and seminal quality and oocyte fertilization were analyzed. Subsequently, a portion of each semen sample was cryopreserved and, after two days, the oocytes from three new females were fertilized with cryopreserved semen from the males. The analyzes showed that progressive motility, spermatic vigor, motility duration, number of normal sperm and secondary abnormalities were higher in fresh semen than in semen after thawing (P <0.0001). Similarly, fertilization and hatching rates and the percentage of normal and abnormal larvae in fertilized oocytes were higher when fresh semen was used (P <0.0001). The cryopreservation process affected the qualitative parameters of the semen of Piaractus mesopotamicus. The primary abnormality of spermatozoa was the main variable that influenced both fertilization and hatching rates, both in fresh and thawed semen. The second most important variable that influenced, particularly, thawed semen, was the spermatic vigor.

Cryopreservation of mammal embryos has been technically feasible for many years, but morphological injuries still persist in fish embryos during cryopreservation. Thus, the objective of the present study was to describe these freezing injuries in Piaractus mesopotamicus embryos. Two hundred and twenty-five embryos were collected at the post-gastrula stage and assigned into four treatments of sucrose at 8.5, 17.0, 25.0 or 34.0% plus 9.0% methanol. The control was prepared with distilled water only. The gradual decrease in the temperature was 0.5°C/min. After the seeding stage, the fish embryos were stored in liquid nitrogen at -33°C. Thereafter, they were thawed for evaluating per cent hatching, and the samples collected from every treatment were submitted to scanning electron microscopy for morphological analysis. The micrographic images showed that there was substantial alterations in embryo morphology under the highest concentrations of sucrose. These solutions did not prevent the formation of ice crystals, which lead to deformities and killed the embryos, but the observed reduced level of morphological structure in these embryos when treated with 17.0% sucrose plus 9.0% methanol is a compelling argument for additional studies.

Cryopreservation of germplasm provides a promising method to preserve fish genetic material, which is of great importance in preservation of species diversity, aquaculture, and management of fish models used in biomedical research. In the present study, cryopreservation of Rhinelepis aspera embryos, a Brazilian endangered species, was studied for the first time using a short-term cooling protocol. Embryos at blastoporous closing stage were selected, placed in 6-ml glass vials and stored at -8 °C for 6 h in 10 different cryoprotectant solutions: S1 (17.1% sucrose + 9% methanol); S2 (17.1% sucrose + 9% DMSO); S3 (8.5% sucrose + 8.5% glucose + 9% methanol); S4 (8.5% sucrose + 8.5% glucose + 9% DMSO); S5 (17.1% sucrose + 9% ethylene glycol); S6 (8.5% sucrose + 8.5% glucose + 9% ethylene glycol); S7 (17.1% sucrose + 4.5% methanol + 4.5% DMSO); S8 (17.1% sucrose + 4.5% methanol + 4.5% ethylene glycol); S9 (17.1% sucrose + 4.5% DMSO + 4.5% ethylene glycol); and S10 (100% water). Embryo viability was assessed by hatching rate, counting live larvae and number of failed eggs under a stereomicroscope. The results showed that only the cryoprotectant solutions that contained methanol associated to sucrose (S1, S7 and S8) provided partial protection of Rhinelepis aspera embryos from cold damage (over 50% hatching rate in S1), while the use of DMSO and ethylene glycol, isolated or in combination, resulted in no hatching rate. Further studies are needed in order to extend the storage time and to improve the hatching rate for the species.

Although the sperm cryopreservation of freshwater and marine teleosts has been feasible for years, the cryopreservation of some fish embryos still remains elusive. Thus, the objective of this experiment was to analyze the embryo morphology after freezing and thawing 40 embryos of Piaractus mesopotamicus immersed into methanol and ethylene glycol, both at 7, 10 and 13% plus 0.1 M sucrose for 10 min. Soon after thawing, three embryos were treated with historesin, stained with hematoxylin-eosin and analyzed under an optical microscope. From every treatment, one palette containing embryos was thawed and incubated, but none of the eggs hatched. Samples containing two embryos were immersed into 10% methanol or 10% ethylene glycol both in association with sucrose, and embryos immersed into only water or sucrose solution were frozen, processed and analyzed using scanning electron microscopy (SEM). In both cases, the control group was immersed into only water. Although the embryos had the chorion, vitello, yolk syncytial layer and blastoderm, all of them were found altered under the optical microscope and by SEM. The chorion was irregular and injured; there was no individuality in the yolk granules; the yolk syncytial layer had an irregular shape, thickness and size; the blastoderm showed injuries in the nucleus shape and sometimes was absent; the blastoderm was located in atypical areas and absent in some embryos. In conclusion, no treatment was effective in preserving the embryos, and none of the embryos avoided injury from intracellular ice formation. These morphological injuries during the freezing process made the P. mesopotamicus embryos unfeasible for hatching.